For a 22" TFT a video card would yield instant results...does not matter if its ATi or nVidia. Only other route is a C2D 8600 and C2D board....that would clock like mad. So you could get 4Ghz and that would be a massive boost over your AMD. And you could sell your AMD stuff.

BTW....I am saying all this as you stated "GAMING RIG"......depends on what you are willing to spend the rig you have now is quite nice to be honest.